1. Field of the Invention
The disclosure generally relates to a method and system for cooling a heat source. More specifically, the disclosure relates to a method and system for reducing thermal energy of a heat source by transferring energy from the source through charged particles.
2. Description of Related Art
Cryogenic coolers are refrigerators capable of attaining a temperature below 200K (−73 C). Conventional cryogenic coolers are large, mechanical reverse heat engine devices. Examples of such coolers include Stirling, Pulse-Tube, Joule-Thomson, and reverse-Brayton mechanical coolers. Such coolers have many moving parts such as valves, seals, compressors and expanders. Consequently, while conventional coolers provide efficient refrigeration, they have inadequate reliability and limited service life. They also suffer from high levels of vibration and cannot be used with sophisticated infrared (IR) sensors, master oscillators, or low noise amplifiers (LNAs) which require cryogenic system with little or no vibration. The large size of the conventional cryogenic systems also results in a prolonged cool down time which often requires excessive lift capability to meet the cool down requirements.
Conventional mechanical cryogenic coolers do not scale well into the 100 to 300 milliwatt cooling realm, and in the cooling of modern sensors and microcircuits the conventional coolers are many orders of magnitude larger in footprint or occupied volume than the integrated circuit (IC) being cooled. Indeed, some cryo-coolers are multistage devices that further complicate the issues of size, weight, reliability and cool-down time.
The thermoelectric effect (TE) is the direct conversion of temperature differences to electric voltage and vice versa. A thermoelectric device creates a voltage when it is supplied with different temperatures on each side thereof. Conversely, when a voltage is applied to the device, it creates a temperature difference. This effect can be used, for example, to generate electricity, measure temperature, and heat or cool objects.
The conversion of energy from thermal state to electrical state (the thermoelectric phenomenon) has been described in view of Seebeck effect, the Peltier effect and the Thomson effect. The Thomson effect occurs in a conductor when the ends of that conductor are at different temperatures and an electric current is flowing, generating a heating that is different than I2R heating, the difference being dependent on the magnitude and direction of the current, the temperature, and on the material. The Peltier effect describes the isothermal heat exchange that takes place at the junction of two different materials when an electrical current flows between them. The rate of development of heat is greater or less than that of I2R heating, the difference depending upon the direction and magnitude of the electric current, on the temperature, and on the two materials forming the junction. The Seebeck effect can be viewed as the sum of the Peltier and Thomson effects around a circuit loop.
The Peltier effect is caused by the fact that the electron's average energy varies from material to material. Thus, when a charged carrier such as an electron or a hole crosses from one material to another, the charged carrier compensates for the energy difference by exchanging heat with the surrounding lattice. The amount of heat exchanged for a given current I across a junction is determined by the Peltier coefficient. The Peltier coefficient is negative if heat is transported by the electrons and it is positive if heat is transported by holes.
Thus, when a semiconductor material is placed between a heat source and a heat sink, a favorable current flow through the semiconductor causes the heat to be extracted from the heat source and deposited on the heat sink. Applying these principles, conventional systems have been devised to provide solid state cooling, typically for electronic devices. However, conventional systems have been inefficient in their capacity to conduct heat. Accordingly, there is a need for an efficient solid state cooling system.